This is the first book to introduce the full spectrum of security and risks and their management. Author and field expert Bruce Newsome helps readers learn how to understand, analyze, assess, control, and generally manage security and risks from the personal to the operational. They will develop the practical knowledge and skills they need, including analytical skills, basic mathematical methods for calculating risk in different ways, and more artistic skills in making judgments and decisions about which risks to control and how to control them.

Probability and Uncertainty

Probability and uncertainty

The concepts of risk and hazard inherently include the concept of uncertainty: Risk is potential returns, and a hazard is a potential threat. This potential is a type of uncertainty. The sections of this chapter describe uncertainty and probability, including practical methods for identifying and assessing them.


This section defines uncertainty, explains the difference between uncertainty and probability, explains the difference between uncertainty and risk, and introduces some practical ways to identify uncertainties.

Defining Uncertainty

Uncertainty is a lack of certainty, where certainty is “the personal quality of being completely sure” (FrameNet). Many other definitions would suggest that uncertainty, probability, and risk can be the same (see Pedagogy Box 6.1), but they are distinct, with important implications for how we assess and ...

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